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A piezoelectric actuator is described as including a vibration plate in
which grooves associated with respective pressure chambers are formed on
a surface of the vibration plate, and a piezoelectric layer on the
surface of the vibration plate on an opposite side of a channel unit.
Since grooves corresponding to the grooves in the vibration plate are
formed also in the piezoelectric layer, it is possible to reduce a cross
talk between operating sections of the piezoelectric layer. Further,
chips and cracks are hardly developed in the piezoelectric layer.

1. A piezoelectric actuator which has a plurality of operating sections,
comprising: a vibration plate having first grooves formed therein, the
first grooves being associated with respective operating sections,
respectively; a piezoelectric layer which is provided on the vibration
plate, and has second grooves formed therein, the second grooves
corresponding to the first grooves in the vibration plate, and in which a
thickness of the piezoelectric layer in the second grooves is less than a
thickness of the piezoelectric layer in an area in which no second groove
are formed; and individual electrodes which are provided on the operating
sections of the piezoelectric layer, respectively, and which supply a
drive voltage to the operating sections, respectively.

2. The piezoelectric actuator according to claim 1, wherein each of the
grooves is provided for one of the operating sections.

3. The piezoelectric actuator according to claim 1, wherein each of the
grooves is provided between adjacent operating sections among the
plurality of operating sections.

4. The piezoelectric actuator according to claim 1, wherein the vibration
plate is an electrode which is common for the operating sections.

5. The piezoelectric actuator according to claim 1, wherein the thickness
of the piezoelectric layer in the second grooves is less than a depth of
the first grooves.

6. A liquid transporting apparatus comprising: a channel unit including a
plurality of pressure chambers formed therein, each of the pressure
chambers having a supply port and a discharge port which discharges a
liquid; and a piezoelectric actuator as defined in claim 1 wherein the
vibration plate is provided on the channel unit to cover the pressure
chambers.

7. The liquid transporting apparatus according to claim 6, wherein the
grooves are provided for each of the pressure chambers.

8. The liquid transporting apparatus according to claim 6, wherein the
vibration plate is an electrode which is common for the pressure
chambers.

9. The liquid transporting apparatus according to claim 6, wherein the
thickness of the piezoelectric layer in the second grooves is less than a
depth of the first grooves.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Divisional application of co-pending U.S.
application Ser. No. 11/213,826, filed Aug. 30, 2005, which is a
Nonprovisional application claiming priority under 35 U.S.C. .sctn.
119(a) on Patent Application No. 2004-251438, filed in Japan on Aug. 31,
2004, the entire contents of these applications are hereby incorporated
by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a piezoelectric actuator, a liquid
transporting apparatus, and a method of manufacturing liquid transporting
apparatus, and in particular to a piezoelectric actuator, a liquid
transporting apparatus, and a method of manufacturing liquid transporting
apparatus in which a cross talk between a plurality of operating sections
is reduced.

DESCRIPTION OF THE RELATED ART

[0003] An ink-jet head which discharges ink from a nozzle onto a recording
paper is an example of a liquid transporting apparatus which discharges
liquid onto an object subjected to discharge. This ink-jet head includes
a channel unit which has an ink-discharge channel including a pressure
chamber which communicates with the nozzle, and a piezoelectric actuator
which causes an ink to be discharged from the nozzle by changing a volume
of the pressure chamber. In this case, a general piezoelectric actuator
includes a vibration plate which is positioned oppose to the pressure
chamber, a piezoelectric element which is formed of a material such as
lead zirconate titanate (PZT) and arranged on a surface of the vibration
plate, and an individual electrode which is formed in an area facing the
pressure chamber on a surface of the piezoelectric element. The
piezoelectric actuator is structured such that when a drive voltage is
applied to the individual electrode, an electric field is generated in
the piezoelectric element positioned corresponding to the individual
electrode, the piezoelectric element and the vibration plate are deformed
partially so as to apply pressure on ink in the pressure chamber.

[0004] In such ink-jet head, for realizing both of high quality of
recording image and the reduction of the size of the head, there is a
tendency that a plurality of nozzles are arranged closely. However, when
an attempt is made to arrange a large number of nozzles very closely, it
is necessary to arrange a plurality of pressure chambers closely, too.
Therefore, when a voltage is applied to an individual electrode facing a
certain pressure chamber and the piezoelectric element to deform the
vibration plate, this deformation is propagated even to a piezoelectric
element and a vibration plate of an area corresponding to an adjacent
pressure chamber, which in turn causes a phenomenon (a so-called cross
talk) which destabilizes the ink-discharge characteristics of a nozzle
communicating with the adjacent pressure chamber. As a result the
negative effect exerted on a printing quality cannot be neglected. More
specifically, due to the cross talk, there is an increased variation in a
speed of the ink droplet discharged from each of the nozzles or a
decrease of discharge stability.

[0005] In view of the situation, an ink-jet head is disclosed in Japanese
Patent Application Laid-open No. 2-187352 and Japanese Patent No.
3152260. In this ink-jet head, a groove is formed by a dicing process in
an area of the piezoelectric element and the vibration plate, which does
not overlap with the pressure chamber, with the piezoelectric element
joined to a surface of the vibration plate, so that the deformation of
the piezoelectric element and the vibration plate is hardly propagated
between the adjacent pressure chambers.

[0006] Japanese Patent Application Laid-open No. 2-187352 discloses
laminating a piezoelectric element on the vibration plate before forming
a groove in the vibration plate and cutting the piezoelectric element and
the vibration plate simultaneously so that the groove is formed in the
vibration plate. The obtained head has a structure in which the
piezoelectric element is divided into individual piezoelectric elements
with a plurality of the grooves intervening therebetween in the vibration
plate, as shown in FIGS. 1 and 2 of this patent document.

[0007] Japanese Patent No. 3152260 discloses, to prevent the cross talk,
laminating the vibration plate and the piezoelectric element on the
pressure chamber and then cutting simultaneously the piezoelectric
element and the vibration plate so that a groove is formed which extends
to a side wall of the pressure chamber. The obtained head has a structure
in which not only the piezoelectric element but also the vibration plate
are divided for each of the pressure chambers, as shown in FIGS. 1 to 4
of Japanese Patent No. 3152260.

SUMMARY OF THE INVENTION

[0008] In ink-jet heads according to the patent documents described above,
when a large number of pressure chambers is arranged closely, it is
necessary to form a groove with a very high accuracy so that a groove is
not formed even in an area of a piezoelectric layer and a vibration
plate, facing a pressure chamber. However, if an attempt is made to form
this groove by a mechanical process such as dicing, the manufacturing
cost of the ink-jet head becomes very high. In a conventional ink-jet
head, a piezoelectric element is formed by baking a green sheet of PZT.
However, if the groove is formed by a mechanical process on the
piezoelectric element after baking, a chip or a crack tend to occur in
the piezoelectric element, due to which there is a decline in yield
during the manufacturing process, and a tear is developed in the chipped
or cracked piezoelectric element by repeating recording operations,
thereby deteriorating the reliability of discharge.

[0009] In addition, in a structure in which a piezoelectric element is cut
and isolated for each pressure chamber as disclosed in the patent
documents described above, the piezoelectric element easily exfoliates
from the vibration plate during driving of the piezoelectric element.

[0010] A first object of the present invention is to provide a
piezoelectric actuator, a liquid transporting apparatus and a method of
manufacturing liquid transporting apparatus which is capable of forming a
groove for reducing a cross talk in the vibration plate and the
piezoelectric layer while maintaining a high yield and a low
manufacturing cost. A second object of the present invention is to
provide a piezoelectric actuator, a liquid-jet apparatus, and a method of
manufacturing liquid-jet apparatus which is capable of preventing the
exfoliation of the piezoelectric layer while preventing the cross talk in
portions of the piezoelectric layer corresponding to adjacent pressure
chambers.

[0011] According to a first aspect of the present invention, there is
provided a method of manufacturing a liquid transporting apparatus
including a channel unit in which a plurality of pressure chambers
communicating with a discharge port which discharges a liquid are
arranged along a flat surface; and a piezoelectric actuator which
includes a vibration plate which is joined to one surface of the channel
unit to cover the pressure chambers, and a piezoelectric layer formed of
a piezoelectric material, and which changes selectively a volume of the
pressure chambers, the method comprising: a step of providing, on the
channel unit, a vibration plate having grooves formed on a surface
thereof, the grooves being associated with the respective pressure
chambers; and a piezoelectric layer forming step of forming the
piezoelectric layer by depositing particles of a piezoelectric material
on the surface of the vibration plate on which the grooves have been
formed. The grooves associated with the respective pressure chambers may
be connected to form a continuous groove area.

[0012] This liquid transporting apparatus applies pressure on a liquid in
the pressure chamber by changing a volume of the pressure chamber by
partially deforming the vibration plate and the piezoelectric layer in
the area overlapping with the pressure chamber, and discharges the liquid
from a nozzle. During manufacturing of this liquid transporting
apparatus, firstly, a vibration plate which has grooves, associated with
the respective pressure chambers, formed on the surface of the vibration
plate are prepared and the vibration plate is provided on the channel
unit. Next, the piezoelectric layer is formed by depositing the particles
of a piezoelectric material on the surface of the vibration plate on
which the grooves have been formed. At this time, grooves similar to
these grooves on the vibration plate are formed in the piezoelectric
layer at positions corresponding to the grooves formed on the vibration
plate. Therefore, the vibration plate and the piezoelectric layer become
thin in an area between the pressure chambers where the grooves are
formed in the vibration plate. Accordingly, when portions of the
piezoelectric layer and the vibration plate in a position overlapping
with a certain pressure chamber are deformed partially, the deformation
is hardly propagated to another portions of the piezoelectric layer and
the vibration plate in a position overlapping with other pressure
chamber, thereby reducing the cross talk. Moreover, the grooves can be
formed in the piezoelectric layer only by depositing the particles of the
piezoelectric material on the surface of the vibration plate in which the
grooves are formed. Accordingly, as compared to a case of forming the
grooves in the piezoelectric layer by a mechanical process, the grooves
can be formed at a low cost. Furthermore, a chip and a crack are hardly
developed in the piezoelectric layer, thereby improving the yield and the
reliability of discharge.

[0013] Upon providing the grooves in the vibration plate, grooves which
extend along edges of the pressure chambers may be formed in an area on
the surface of the vibration plate on an opposite side of the channel
unit, the area not overlapping with the pressure chambers, or the grooves
in the vibration plate may be formed in an area which overlaps with the
pressure chambers (groove forming step). In the latter case, the grooves
may be formed in an area where the grooves divide the pressure chambers
into a central portion and a peripheral portion. The cross talk can be
prevented effectively by providing the grooves in positions associated
with the pressure chambers. The liquid transporting apparatus may be, for
example, a liquid-jet apparatus, and in this case, the discharge port is
a nozzle which discharges the liquid.

[0014] In the piezoelectric layer forming step of the method of
manufacturing liquid transporting apparatus according to the present
invention, the piezoelectric layer on surfaces of the grooves may be
formed to be thinner than the piezoelectric layer in an area other than
the surfaces of the grooves. Therefore, in addition to the vibration
plate becoming partially thin due to the groove, the piezoelectric layer
formed on the surface of the groove in the vibration plate also becomes
thin. Accordingly, it is possible to further reduce the cross talk.

[0015] In the piezoelectric layer forming step in the method of
manufacturing liquid transporting apparatus of the present invention, the
piezoelectric layer may be formed by a chemical deposition method or an
aerosol deposition method. When the piezoelectric layer is formed by the
chemical deposition method or the aerosol deposition method, the
piezoelectric layer on the surfaces of the grooves can be made easily
thinner than the piezoelectric layer in an area other than the surfaces
of the grooves.

[0016] In the groove forming step of the method of manufacturing liquid
transporting apparatus of the present invention, the grooves may be
formed to substantially surround the associated pressure chambers as
viewed from the direction orthogonal to the flat surface. When the
pressure chambers are respectively surrounded by the grooves, the
deformation of the piezoelectric layer in the area overlapping with one
of the pressure chambers is hardly propagated to an area overlapping with
other pressure chamber, thereby reducing the cross talk assuredly.

[0017] In the groove forming step of the method of manufacturing liquid
transporting apparatus of the present invention, one of the grooves may
be common in an area between two adjacent pressure chambers. Thus, by
forming the grooves commonly between the two pressure chambers, the
number of grooves can be reduced. Further, since the thickness of one
groove becomes greater, it is easy to form the grooves.

[0018] In the method of manufacturing liquid transporting apparatus of the
present invention, the vibration plate may be formed of an
electroconductive metallic material, and the method may further comprise
an individual electrode forming step of forming a plurality of individual
electrodes in an area of the piezoelectric layer, the area overlapping
with the pressure chambers as viewed from a direction orthogonal to the
flat surface, after the piezoelectric layer forming step. Thus, since the
vibration plate is made of the metallic material, the grooves can be
formed easily in the vibration plate by a method such as etching.
Moreover, since the vibration plate is electroconductive, the vibration
plate can be made to function as a common electrode which faces the
individual electrodes and generates an electric field in the
piezoelectric layer. Accordingly, it is possible to omit the common
electrode and to simplify a structure of the piezoelectric actuator.

[0019] In the method of manufacturing liquid transporting apparatus of the
present invention, the vibration plate may be formed of an
electroconductive metallic material, and the method may further comprise:
an insulating film forming step which is a step after the groove forming
step and before the piezoelectric layer forming step, and is a step of
forming an insulating film on the surface of the vibration plate on the
opposite side of the channel unit; an individual electrode forming step
which is a step after the insulating film forming step, and is a step of
forming a plurality of individual electrodes in an area of the insulating
film which overlaps with the pressure chambers as viewed from the
direction orthogonal to the flat surface; and a common electrode forming
step which is a step after the piezoelectric layer forming step, and is a
step of forming a common electrode in an area of the piezoelectric layer
which overlaps with the individual electrodes as viewed from the
direction orthogonal to the flat surface. In this case, since the
vibration plate is made of an electroconductive metallic material, it is
possible to form the groove easily in the vibration plate by a method
such as etching.

[0020] The method of manufacturing liquid transporting apparatus of the
present invention may comprise a joining step which is a step after the
groove forming step and before the piezoelectric layer forming step, and
is a step of joining the vibration plate to the channel unit. The
vibration plate after the grooves have been formed therein in the groove
forming step is susceptible to breaking due to the decline in strength
particularly in portions where the grooves are formed. However, because
the vibration plate is joined to the channel unit before forming the
piezoelectric layer in the surface of the vibration plate, the vibration
plate is reinforced by the channel unit and hardly breaks. Therefore, it
is easy to handle the vibration plate in the piezoelectric layer forming
step.

[0021] According to a second aspect of the present invention, there is
provided a piezoelectric actuator which has a plurality of operating
sections, the piezoelectric actuator comprising: a vibration plate having
first grooves formed therein, the first grooves being associated with
respective operating sections; a piezoelectric layer which is provided on
the vibration plate, and which has second grooves formed therein, the
second grooves corresponding to the first grooves in the vibration plate,
and in which a thickness of the piezoelectric layer in the second grooves
is less than a thickness of the piezoelectric layer in an area in which
no second groove are formed; and individual electrodes which are provided
on the respective operating sections of the piezoelectric layer and which
supply a drive voltage to the respective operating sections.

[0022] According to a third aspect of the present invention, there is
provided a liquid transporting apparatus comprising: a channel unit
including a plurality of pressure chambers formed therein, each of the
pressure chambers having a supply port and a discharge port which
discharges a liquid; a vibration plate which is provided on the channel
unit to cover the pressure chambers, and which has first grooves formed
therein, the first grooves being associated with the respective pressure
chambers; a piezoelectric layer which is provided on the vibration plate
and which has second grooves formed therein, the second grooves
corresponding to the first grooves in the vibration plate, and in which a
thickness of the piezoelectric layer in the second grooves is less than a
thickness of the piezoelectric layer in an area in which no second
grooves are formed; and individual electrodes which are provided on the
piezoelectric layer to supply a drive voltage to the piezoelectric layer
corresponding to the pressure chambers.

[0023] In the piezoelectric actuator and the liquid transporting apparatus
of the present invention, since the firsts groove are formed in the
vibration plate and the second grooves, corresponding to the first
grooves in the vibration plate, are formed in the piezoelectric layer,
the cross talk between the operating sections or between portions of the
piezoelectric layer corresponding to the pressure chambers is effectively
prevented. Moreover, in the second grooves of the piezoelectric layer,
there is remained a portion of the piezoelectric layer having a thickness
less than a thickness of the piezoelectric layer in an area in which no
second grooves are formed. Therefore, the piezoelectric layer is hardly
exfoliated from the vibration plate and a mechanical strength of the
piezoelectric layer can be maintained.

[0024] In the piezoelectric actuator and the liquid transporting apparatus
of the present invention, one of the grooves may be provided for each of
the operating sections or each of the pressure chambers, or one of the
grooves may be common for adjacent operating sections or adjacent
pressure chambers. The grooves may be provided in an area which overlaps
with the operating sections or the pressure chambers, or in an area which
does not overlap with the operating sections or the pressure chambers. In
the piezoelectric actuator or the liquid transporting apparatus of the
present invention, the vibration plate may be an electrode which is
common for the operating sections or the pressure chambers. In the
piezoelectric actuator and the liquid transporting apparatus of the
present invention, the thickness of the piezoelectric layer in the second
grooves is less than a depth of the first grooves.

[0025] The piezoelectric actuator in the present invention may be used in
the liquid transporting apparatus which is represented by an ink-jet
apparatus such as an ink-jet head. Or the piezoelectric actuator in the
present invention can be used as an optical deflector plate or an optical
switch for optical communication by providing an optical element such as
a mirror. Or, the piezoelectric actuator in the present invention can be
used as a display unit in which each of the operating sections is a
pixel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic perspective view of an ink-jet printer
according to an embodiment of the present invention;

[0027] FIG. 2 is a plan view of the ink-jet head;

[0028] FIG. 3 is a partially enlarged plan view of FIG. 2;

[0029] FIG. 4 is a cross-sectional view taken along a line IV-IV shown in
FIG. 3;

[0030] FIG. 5 is a cross-sectional view taken along a line V-V shown in
FIG. 4;

[0038] FIG. 13 is a plan view of an actuator of an ink-jet head of a
second embodiment;

[0039] FIG. 14 is a cross-sectional view taken along a line XIV-XIV shown
in FIG. 13;

[0040] FIG. 15 is a cross-sectional view taken along a line XV-XV shown in
FIG. 13;

[0041] FIG. 16 is a plan view of an actuator of an ink-jet head of a third
embodiment;

[0042] FIG. 17 is a cross-sectional view taken along a line XVII-XVII
shown in FIG. 16;

[0043] FIG. 18 is a cross-sectional view taken along a line XVIII-XVIII
shown in FIG. 16; and

[0044] FIG. 19 is a schematic cross-sectional view of a liquid
transporting apparatus of a fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

[0045] Embodiments of the present invention will be described below. A
first embodiment is an example in which the present invention is applied
to an ink-jet head which discharges ink on a recording paper as a
liquid-jet apparatus.

[0046] Firstly, an ink-jet printer 100 which includes an ink-jet head 1
will be described briefly. As shown in FIG. 1, the ink-jet printer 100
includes a carriage 101 which is movable in a left and right direction in
the drawing (direction indicated by a two-pointed arrow), the ink-jet
head 1 of serial type which is provided on the carriage 101 and
discharges ink onto a recording paper P, and transporting rollers 102
which carry the recording paper P in a forward direction (direction
indicated by a horizontal arrow) in FIG. 1. The ink-jet head 1 moves
integrally with the carriage 101 in a left and right direction (scanning
direction) and discharges ink onto the recording paper P from ejecting
ports of nozzles 20 (refer FIGS. 2 to 5) formed in an ink-discharge
surface of a lower surface of the ink-jet head 1. The recording paper P,
with an image recorded thereon by the ink-jet head 1, is discharged
forward (paper sending direction) by the transporting rollers 102.

[0047] Next, the ink-jet head 1 will be described in detail with reference
to FIGS. 2 to 5. As shown in FIGS. 2 to 4, the ink-jet head 1 includes a
channel unit 2 in which an individual ink passage 21 (refer to FIG. 4)
which includes a pressure chamber 14 inside is formed and a piezoelectric
actuator 3 which is laminated on an upper surface of the channel unit 2.

[0048] The channel unit 2 will be described below. As shown in FIG. 4, the
channel unit 2 includes a cavity plate 10, a base plate 11, a manifold
plate 12, and a nozzle plate 13, and these four plates 10 to 13 are
joined in stacked layers. Among these four plates, the cavity plate 10,
the base plate 11, and the manifold plate 12 are stainless steel plates,
and an ink channel, such as the pressure chamber 14, and a manifold 17
which will be described later, can be formed easily in these plates by
etching. Moreover, the nozzle plate 13 is formed of a high-molecular
synthetic resin material such as polyimide and is joined to a lower
surface of the manifold plate 12. Or the nozzle plate 13 may also be
formed of a metallic material such as stainless steel, similar to the
three plates 10 to 12.

[0049] As shown in FIGS. 2 to 4, in the cavity plate 10, a plurality of
pressure chambers 14 arranged along a flat surface is formed. These
pressure chambers 14 are open in a surface (an upper surface of the
cavity plate 10 to which a vibration plate 30 which will be described
later is joined) of the channel unit 2. Moreover, the pressure chambers
14 are arranged in two rows in the paper feeding direction (vertical
direction in FIG. 2). Each pressure chamber 14 is substantially
elliptical in a plan view and is arranged such that the long axis is the
left and right direction (scanning direction). Moreover, an ink-supply
port 18 which communicates with an ink tank (not shown in the diagram) is
formed in the cavity plate 10.

[0050] As shown in FIG. 3 and FIG. 4, communicating holes 15 and 16 are
formed in the base plate 11 at positions which overlap in a plan view
with both end portions of the associated pressure chamber 14 in the long
axis direction. In addition, in the manifold plate 12, a manifold 17,
which is extended in the paper feeding direction (vertical direction in
FIG. 2) and overlaps with any one of left and right end portions of the
pressure chamber 14 in a plan view in FIG. 2, is formed. Ink is supplied
to the manifold 17 from the ink tank via the ink-supply port 18.
Moreover, a communicating hole 19 is formed at a position which overlaps
in a plan view with an end portion on a side of the pressure chamber 14
opposite to the manifold 17. Furthermore, a plurality of nozzles 20 is
formed in the nozzle plate 13 at positions which overlap in a plan view
with a plurality of communicating holes 19. The nozzle 20 is formed for
example, by means of excimer laser process on a substrate of a
high-molecular synthetic resin such as polyimide.

[0051] As shown in FIG. 4, the manifold 17 communicates with the pressure
chamber 14 via the communicating hole 15, and the pressure chamber 14
communicates with the nozzle 20 via the communicating holes 16 and 19.
Thus, an individual ink channel 21 from the manifold 17 to the nozzle 20
via the pressure chamber 14 is formed in the channel unit 2.

[0052] Next, the piezoelectric actuator 3 will be described below. As
shown in FIGS. 2 to 5, the piezoelectric actuator 3 includes the
vibration plate 30, the piezoelectric layer 31, and a plurality of
individual electrodes 32. The vibration plate which is electroconductive
is arranged on an upper surface of the channel unit 2. The piezoelectric
layer 31 is formed continuously on an upper surface of the vibration
plate 30, spreading across the pressure chambers 14. The individual
electrodes 32 are formed on an upper surface of the piezoelectric layer
31 corresponding to the respective pressure chambers 14.

[0053] The vibration plate 30 is a plate having roughly rectangular shape
in a plan view and is made of a metallic material such an iron alloy like
stainless steel, a copper alloy, a nickel alloy, or a titanium alloy. The
vibration plate 30 is joined in a laminated state to the upper surface of
the cavity plate 10 such that openings of the pressure chambers 14 are
closed. Moreover, the vibration plate 30 positioned facing the plurality
of individual electrodes 32 also serves as a common electrode which
generates an electric field in the piezoelectric layer 31 between the
individual electrode 32 and the vibration plate 30. A groove 36, which
extends along an edge of the pressure chamber 14 and surrounds the
pressure chamber 14 except for an end portion on a side of the manifold
17 of each of the pressure chambers 14, is formed in the upper surface of
the vibration plate 30 (a surface opposite to a surface facing the
channel unit 2) in an area which does not overlap with the pressure
chambers 14 in a plan view. The groove 36 is formed in an area between
the two adjacent pressure chambers 14 and in common for these two
adjacent pressure chambers 14.

[0054] The piezoelectric layer 31 which is composed of mainly lead
zirconate titanate (PZT) which is a solid solution of lead titanate and
lead zirconate, and is a ferroelectric substance is formed on the surface
of the vibration plate 30. The piezoelectric layer 31 is formed
continuously spreading across the pressure chambers 14. A groove 37 which
has a planer shape similar to that of the groove 36 is formed in the
piezoelectric layer 31 at a position facing the groove 36 in the
vibration plate 30. As shown in FIG. 4 and FIG. 5, a thickness of the
piezoelectric layer 31 in this groove 37 is less than a thickness of the
piezoelectric layer 31 in an area where the groove 37 is not formed.

[0055] The plurality of individual electrodes 32 which are elliptic, flat
and smaller in size than the pressure chamber 14 to a certain extent are
formed on a surface of the piezoelectric layer 31. Each of the individual
electrodes 32 is formed at a position overlapping with a central portion
of the corresponding pressure chamber 14 in a plan view. The individual
electrodes 32 are made of an electroconductive material such as gold.
Furthermore, on the surface of the piezoelectric layer 31, a plurality of
terminal sections 35 which are respectively connected to the individual
electrodes 32 are formed at positions partially overlapping with end
portions which are not surrounded by the grooves 37 of the pressure
chambers 14. These terminal sections 35 are connected electrically to a
driver IC (omitted in the diagram) via a flexible wiring member such as a
flexible printed circuit board, and a drive voltage is selectively
supplied to the individual electrodes 32 from the driver IC via the
terminal sections 35.

[0056] Next, an action of the piezoelectric actuator 3 will be described.
When a drive voltage is selectively applied from the driver IC to the
individual electrodes 32, the electric potential of the individual
electrode 32 disposed on the upper side of the piezoelectric layer 31 to
which the drive voltage is supplied differs from the electric potential,
which is held at a ground potential, of the vibration plate 30 which
serves as the common electrode on a lower side of the piezoelectric
layer, and thus an electric field is generated in a vertical direction of
a part of the piezoelectric layer 31 which is sandwiched between the
individual electrode 32 to which the drive voltage is applied and the
vibration plate 30. As the electric field is generated, the part of the
piezoelectric layer, disposed directly below the individual electrode 32
to which the drive voltage is applied, contracts in a horizontal
direction which is orthogonal to a vertical direction in which the
piezoelectric layer 31 is polarized. At this time, since the vibration
plate 30 is deformed due to the horizontal contraction of the
piezoelectric layer 31 so as to project toward the pressure chamber 14, a
volume inside the pressure chamber 14 decreases and a pressure is applied
on the ink in the pressure chamber, thereby discharging the ink from the
nozzle 20 communicating with the pressure chamber 14. Each of the parts
sandwiched between the respective individual electrodes 32 and the
vibration plate 30 functions as an operating section of the piezoelectric
actuator.

[0057] As shown in FIG. 2, in the ink-jet head 1 of the first embodiment,
the pressure chambers 14 are arranged closely along a flat surface. When
a drive voltage is applied to an individual electrode 32 corresponding to
a certain pressure chamber 14, and a part of the piezoelectric layer 31
at a position overlapping with this pressure chamber 14 is deformed, a
so-called phenomenon of cross talk, in which the deformation is
propagated to parts of the vibration plate 30 and the piezoelectric layer
31 overlapping with an adjacent pressure chamber 14, tends to occur.
However, as described above, the grooves 36 and 37, which extend along
the edge of each of the pressure chambers 14 and roughly surround each of
the pressure chambers 14 are formed respectively in the area of the
vibration plate 30 and the piezoelectric layer 31 which do not overlap
with the pressure chamber in a plan view. In the area where these grooves
36 and 37 are formed, the thicknesses of the vibration plate 30 and the
piezoelectric layer 31 are respectively less than the thickness in other
area in which no grooves 36 and 37 are formed. Therefore, since the
deformation of the parts of the vibration plate 30 and the piezoelectric
layer 31 respectively overlapping with a certain pressure chamber 14 is
hardly propagated to other parts of the vibration plate 30 and the
piezoelectric layer 31 respectively overlapping with other adjacent
pressure chamber 14, it is possible to prevent the cross talk assuredly.
Moreover, the piezoelectric layer 31 exists also at a bottom of the
groove 37. In other words, the piezoelectric layer 31 is not cut and
isolated for each of the operating sections but maintains a continuous
form. Therefore, as compared to a case in which operating sections of the
piezoelectric layer are cut and isolated from each other, the
piezoelectric layer 31 is hardly exfoliated from the vibration plate 30
and the mechanical strength and the durability of the piezoelectric layer
31 is improved.

[0058] In an area where the grooves 36 and 37 of the vibration plate 30
and the piezoelectric layer 31 are respectively formed, a thickness of
the piezoelectric layer 31 which is deposited in the deepest portion of
the groove 37 is less than a depth of the deepest portion of the groove
37. For this reason, when the part of the piezoelectric layer 31, which
is sandwiched between the individual electrode 32 and the vibration plate
30 serving as a common electrode, operates as in the first embodiment,
displacement of the piezoelectric layer 31 deposited in the groove 37 due
to an effect of the leakage electric field is reduced, thereby further
preventing the cross talk and the decline in drive efficiency.

[0059] Next, a method of manufacturing the ink-jet head 1 will be
described. As shown in FIG. 6A, among the plates 10 to 13 in the channel
unit 2, except the nozzle plate 13 which is made of a synthetic resin,
the three metal plates, i.e. the cavity plate 10, the base plate 11, and
the manifold plate 12 are joined. On the other hand, the grooves 36
described above, which extend along the edge of the pressure chambers 14
and which roughly surround the pressure chambers 14, are formed (groove
forming step) in an area on the upper surface of the vibration plate 30
(a surface opposite to the surface which is joined to the channel unit
2), the area not overlapping in a plan view with the associated pressure
chambers 14. Here, since the vibration plate 30 is made of a metallic
material such as stainless steel, the grooves 36 can be formed easily by
etching or pressing. Moreover, since the vibration plate 30, positioned
facing the plurality of individual electrodes 32, also serves as a common
electrode which generates an electric field in the piezoelectric layer
31, it is not necessary to provide separately a common electrode in
addition to the vibration plate 30, and the structure of the
piezoelectric actuator 3 is simplified.

[0060] Further, the vibration plate 30 having the grooves 36 formed
therein is joined to an upper surface of the cavity plate 10 so that the
pressure chambers 14 are covered (joining step). The joining step is
performed by using an adhesive or by diffusion joining. Here, the
vibration plate 30 after the grooves 36 have been formed therein in the
above-mentioned groove forming step tends to break due to decline in
strength, particularly in portions formed with the grooves 36. However,
because the vibration plate 30 is joined to the cavity plate 10 on an
uppermost layer of the channel unit 2 before forming the piezoelectric
layer 31 in the surface of the vibration plate 30, the vibration plate 30
is reinforced by the channel unit 2 (cavity plate 10) and hardly breaks,
and handling of the vibration plate 30 in a piezoelectric layer forming
step which will be described later becomes easy.

[0061] Next, as shown in FIG. 6B, the piezoelectric layer 31 is formed on
a surface of the vibration plate 30 on the opposite side of the channel
unit 2 (piezoelectric layer forming step). Here, in this piezoelectric
layer forming step, the piezoelectric layer 31 is formed by depositing
particles of PZT on the surface of the vibration plate 30 by a method
such as chemical vapor deposition (CVD) method, aerosol deposition (AD)
method. At this time, the area of the vibration plate 30 where the
grooves 36 have been formed has a recessed form, on which the grooves 37
having a planer shape similar to the grooves 36 are to be formed.

[0062] Here, as an example of a case of forming the piezoelectric layer by
using chemical vapor deposition (CVD) method, a case using a metal
organic chemical vapor deposition (MOCVD) method of forming a thin film
by dissolving a raw material in an organic solvent, and vaporizing the
material, and allowing a gas phase reaction to occur on a surface
subjected to processing will be described below. Materials such as lead
bismuth (dipivaloylmethanato) (Pb(DPM).sub.2), zirconium tetrakis
(dipivaloylmethanato) (Zr(DPM).sub.4), and titanium (di-isopropoxy
dipivaloylmethanato) (Ti(iPrO).sub.2(DPM).sub.2) can be used as the raw
material (for example, see Japanese Patent Application Laid-open
Publication No. 2004-79695). When the vibration plate 30 is heated to
about 600.degree. C., the gas phase reaction occurs between the
above-described materials on the surface of the vibration plate 30, and
the piezoelectric layer 31 of lead zirconate titanate (PZT) is formed on
the surface of the vibration plate 30. Here, as shown in FIG. 7, a raw
material gas is hardly supplied to a space inside the groove 36 formed in
the vibration plate 30, as compared to a surface of the vibration plate
30 in which the groove 36 is not formed. Therefore, since a speed of
formation of the piezoelectric layer 31 on the surface of the groove 36
becomes slow, a thickness Tc of the piezoelectric layer 31 in the groove
37 becomes less than a thickness Ta of the piezoelectric layer 31 in
other area of the piezoelectric layer 31 where the groove 37 is not
formed.

[0063] Moreover, in a case of forming the piezoelectric layer 31 by
aerosol deposition (AD) method in which ultra fine particles are
deposited by colliding the particles onto a surface subjected to
processing at high speed, a proportion of rebounded fine particles, which
do not contribute to the film forming, in an inner surface of the groove
36 of the vibration plate 30 becomes high. Accordingly, in the inner
surface of the groove 36, the particles are not deposited easily as
compared to other surface of the vibration plate 30, and the thickness Tc
of the piezoelectric layer 31 in the groove 37 becomes less than the
thickness Ta of the piezoelectric layer in the area where the groove 37
is not formed.

[0064] Thus, by using the chemical vapor deposition (CVD) method or the
aerosol deposition (AD) method, the piezoelectric layer 31 on the surface
of the groove 36 can be formed to be thinner than the piezoelectric layer
31 in the area where the groove 36 is not formed. Accordingly, the
thickness of the piezoelectric layer 31 and the vibration plate 30 in the
area in which the grooves 36 and 37 are formed is further reduced, and
thus it is possible to reduce the cross talk assuredly. An intermediate
layer made of titanium, platinum, and chromium etc. may be formed between
the vibration plate 30 and the piezoelectric layer 31 by a method such as
sputtering method and vapor deposition method.

[0065] Thus, after the piezoelectric layer 31 is formed on the surface of
the vibration plate 30, an annealing treatment for ensuring sufficient
piezoelectric characteristics in the piezoelectric layer 31 is carried
out, and then, as shown in FIG. 6C, the individual electrodes 32 are
formed by using a method such as screen printing, vapor deposition method
or sputtering method on the surface of the piezoelectric layer 31 in an
area which overlaps in plan view with the pressure chambers 14
(individual electrode forming step). Finally, the nozzle plate 13 made of
a synthetic resin is joined to a lower surface of the manifold plate 12
and the manufacture of the ink-jet head 1 is completed.

[0066] In the steps of manufacturing the ink-jet head 1 described above,
after the vibration plate 30 having the grooves 36 formed therein is
joined to the cavity plate 10 which is a part of the channel unit 2,
another metallic plate (base plate 11 or the manifold plate 12) which is
a part of the channel unit 2 may be joined to the cavity plate 10. Or,
when the nozzle plate 13 is a metallic plate made of stainless steel
etc., before joining the vibration plate 30 and the cavity plate 10, the
channel unit may be formed first by joining the nozzle plate 13 and the
other three metallic plates (cavity plate 10, base plate 11, and manifold
plate 12). Or, the grooves 36 may be formed in the surface of the
vibration plate 30 after joining the channel unit 2 (or the cavity plate
10 in the channel unit 2) and the vibration plate 30. Or, the channel
unit 2 (or the cavity plate 10 in the channel unit 2) and the vibration
plate 30 may be joined after forming the individual electrodes 32, the
piezoelectric layer 31, and the grooves 36 in the vibration plate 30. In
this case, it is desirable to perform the joining by using an adhesive
rather than by diffusion joining.

[0067] According to the method of manufacturing the ink-jet head 1
described above, the following effects can be achieved. In the groove
forming step, the grooves 36 are formed in an area on the surface of the
vibration plate 30 on the opposite side of the channel unit 2, the
grooves 36 extending along the edge of each of the pressure chambers 14,
and the area not overlapping in a plan view with the pressure chambers
14, and then in the piezoelectric layer forming step, the piezoelectric
layer 31 is formed by depositing the particles of the piezoelectric
element on the surface of the vibration plate 30. Therefore, in the area
of the vibration plate 30 where the grooves 36 are formed, the grooves 37
are formed also in the area of the piezoelectric layer 31. Since the
areas of the vibration plate 30 and the piezoelectric layer 31 formed
with the grooves 36 and 37, respectively, are partially thinned (reduced
thickness), the deformation of the piezoelectric layer 31 and the
vibration plate 30 at a position facing a certain pressure chamber 14 is
hardly propagated to the piezoelectric layer 31 and the vibration plate
30 at a position facing other pressure chamber 14, and the cross talk can
be reduced. Moreover, the grooves 37 can be formed in the piezoelectric
layer 31 only by depositing the particles of a piezoelectric material on
the surface of the vibration plate 30 in which the grooves 36 have been
formed. Therefore, as compared to a case of forming grooves in the
piezoelectric layer 31 by a mechanical process, the manufacturing cost
can be reduced and a chip or a crack is hardly developed in the
piezoelectric layer 31 in the area where the grooves 37 are formed, and
it is possible to improve the yield and reliability of discharge.

[0068] In the groove forming process, the groove 36 is formed so as to
almost surround one of the pressure chambers 14. Therefore, the
deformation of the piezoelectric layer 31 in the area overlapping in plan
view with the pressure chamber 14 surrounded by the groove 36 is hardly
propagated to an area overlapping with the other pressure chamber 14,
thereby reducing the cross talk assuredly. Further, the groove 36 is
formed between two adjacent pressure chambers 14 in common for these two
adjacent pressure chambers 14 (refer to FIG. 2 and FIG. 3). Therefore,
the number of grooves 36 can be reduced and since the thickness of the
groove 36 becomes greater, thereby making the forming of the grooves 36
more easily.

[0069] In the piezoelectric layer forming step, the piezoelectric layer 31
on the surfaces of the grooves 36 in the vibration plate 30 is formed to
be thinner than the piezoelectric layer 31 in the area where no groove 36
are formed. Therefore, the thickness of the piezoelectric layer 31 and
the vibration plate 30 in the portion where the grooves 36 are formed is
further decreased, thereby reducing the cross talk more assuredly. The
piezoelectric layer 31 is not cut and isolated for each of the operating
sections, but maintains a continuous form. Therefore, as compared to a
case where the piezoelectric layer 31 is cut and isolated for each of the
operating sections, the piezoelectric layer 31 is hardly exfoliated from
the vibration plate 30 and the mechanical strength and the durability of
the piezoelectric layer 31 is improved.

Second Embodiment

[0070] In the piezoelectric actuator of the ink-jet head in the first
embodiment, the grooves are formed in the area of the vibration plate
which does not overlap with the pressure chambers, but in a piezoelectric
actuator of an ink-jet head in a second embodiment, the grooves are
formed in the area of the vibration plate which overlaps with the
pressure chambers 14. In a piezoelectric actuator 103 of the ink-jet head
101 in the second embodiment, a groove 136 formed in a vibration plate
130 is provided at a position which overlaps with a circumferential
portion of each of the pressure chambers 14 as shown in FIGS. 13 to 15
(plan view in FIG. 13). Therefore, a groove 137 corresponding to each of
the grooves 136 in the vibration plate 130 is formed in a piezoelectric
layer 131 which is formed on the vibration plate 130. The groove 137 in
the piezoelectric layer 131 is also provided at a position which overlaps
with one of the pressure chambers 14, and in particular with a
circumferential portion of the pressure chamber 14. Thus, even if the
groove 136 in the vibration plate 130 is formed in the area overlapping
with the pressure chamber 14, it is possible to prevent the cross talk
with the adjacent pressure chamber 14. Since a structure of the channel
unit 2 and the individual electrodes 32 in the ink-jet head 101 is
similar to the structure in the first embodiment, the description of the
structure is omitted.

Third Embodiment

[0071] In a third embodiment also, an example of an ink-jet head which
includes a piezoelectric actuator in which the groove in the vibration
plate is formed in an area overlapping with each of the pressure chambers
is described. Particularly, in a piezoelectric actuator 203 of this
ink-jet head 201, a groove 236 formed in a vibration plate 230 is
provided so that the groove 236 surrounds a central portion of each of
the pressure chambers 14 as shown in FIGS. 16 to 18 (plan view in FIG.
16). In other words, the grooves are provided so as to divide the area on
the vibration plate corresponding to the piezoelectric layer between the
central portion and a peripheral portion. Therefore, a groove 237
corresponding to each of the grooves 236 in the vibration plate 230 is
formed in a piezoelectric layer 231 which is formed on the vibration
plate 230. Individual electrodes 134 are formed to circumvent the grooves
237 on the piezoelectric layer, leaving the grooves 37 uncovered. The
grooves 236 and 237 formed in such manner are provided on all the
pressure chambers 14 to lower the rigidity in the central portion of the
actuator (namely, the central portion of the area on the vibration plate
and the corresponding portion of the piezoelectric layer thereto),
thereby decreasing the reaction force acting on the joining portion of
the vibration plate to the cavity plate and the corresponding portion of
the piezoelectric layer to the joining portion when the piezoelectric
actuator is driven. Accordingly, it is possible to avoid the cross talk
with the respective adjacent pressure chambers 14. Moreover, a structure
in which the groove 236 in the vibration plate 230 surrounds the central
portion of one of the pressure chambers 14 has been disclosed by the
applicant in US Patent Application Publication No. 2003/0107622A1
(corresponding to Japanese Patent Application Laid-open No. 2004-166463)
and US Patent Application Publication No. 2005/0069430A1 (corresponding
to Japanese Patent Application Laid-open No. 2005-105892), which has an
advantage to simplify the driving of the piezoelectric actuator owing to
a relationship with a drive voltage obtained, by forming the grooves 236
in such positions. Since a structure of the channel unit 2 etc. in the
ink-jet head 201 is similar to the structure in the first embodiment, the
description of the structure is omitted. The contents of the US Patent
Application Publication Nos. 2003/0107622A1 and 2005/0069430A1 have been
incorporated herein by reference.

Fourth Embodiment

[0072] In a fourth embodiment, an example in which the present invention
is applied to a liquid transporting apparatus will be described. A liquid
transporting apparatus 800 includes a first transporting section 820 and
a second transporting section 840 which are capable of transporting
different liquids respectively. Each of the transporting sections
includes a channel unit 802 which has a pressure chamber 824 formed
therein, a piezoelectric actuator 803 which is provided on the channel
unit 802 so as to cover the respective pressure chambers 824, and liquid
tanks 850 which accommodate liquids L1 and L2, respectively. The channel
unit 802 has a cavity plate 810 and a base plate 811 as shown in FIG. 19.
The pressure chambers 824 are formed in the cavity plate 810 and the base
plate 811 has inlet channels 812 and outlet channels 813 which
communicate respectively with the pressure chambers

[0073] 824. The inlet channel 812 communicates with the liquid tank 850
via a supply-side tube 812a. Moreover, a discharge-side tube 813b is
fitted to the outlet channel 813 and the discharge-side tube 813b is
connected to a discharge destination which is not shown in the diagram.
Non-return valves 814 and 815 are fitted to the supply-side tube 812a and
the discharge-side tube 813b respectively. The piezoelectric actuator 803
is similar to the piezoelectric actuator 3 described in the first
embodiment and includes a vibration plate, a piezoelectric layer, a
common electrode, and individual electrodes. Grooves are formed in the
vibration plate and the piezoelectric layer to divide the respective
pressure chambers. When the piezoelectric actuator 803 is operated and a
volume of the pressure chambers 824 is changed, a pressure difference is
developed between the pressure chamber 824 and the liquid tank 850. As a
result of this, the liquid L1 (or L2) is supplied from one of the liquid
tanks 850 to the associated pressure chamber 824 via the inlet channel
812 and the supply-side tube 812a. On the other hand, the liquid L1 (or
L2) in the pressure chambers 824 is discharged via the outlet channel 813
and the outlet-side tube 813b. At this time, by providing the non-return
valves 814 and 815, a reverse flow of the liquid to the ink tank 850 is
prevented and the liquid is carried assuredly from the liquid tank 850 to
the discharge destination.

[0074] The liquids L1 and l2 have different colors and different
compositions, and only a desired liquid can be discharged (transported)
selectively by driving a piezoelectric actuator of a section selected by
a user. In this example, an example of a liquid transporting apparatus
which includes two transporting sections is described, but three or more
of transporting sections may also be provided. Equipments at a site where
the liquid transporting apparatus 800 is used may be used as the liquid
tanks 850, the non-return valves 814 and 815, the supply-side tubes 812a
and the discharge-side tubes 813b. Therefore, the liquid tanks 850, the
non-return valves 814 and 815, the supply-side tubes 812a and the
discharge-side tubes 813b are not necessarily required for the liquid
transporting apparatus 800. Moreover, the liquid tank 850 of the first
transporting section 820 and the liquid tank 850 of the second
transporting section 840 may be common for these transport sections and
the same liquid may be supplied to the pressure chambers of the
respective sections.

[0075] The liquid transporting apparatus in the present invention enables
to transport a liquid selectively via a plurality of liquid discharge
outlets with a simple structure without any cross talk developed between
the adjacent pressure chambers. This liquid transporting apparatus can be
used as a unit module for circulating cooling water in a cooling water
channel which is formed in an electric circuit board. Moreover, since the
liquid transporting apparatus in the present invention can be used as a
micro pump which transports a plurality of liquids, it is possible to
supply a plurality of types of medicines in a predetermined quantity to
patient's body and with a predetermined time schedule.

[0076] Next, modified embodiments in which various modifications are
incorporated in the embodiments, particularly the above-described first
embodiment, will be described. Same reference numerals are used for
components which have a structure identical to a structure in the
embodiments described above, and the description of such components is
omitted.

First Modified Embodiment

[0077] The groove in the vibration plate is not restricted to have a shape
as in the embodiments described above. For example, instead of forming a
groove 37A for the piezoelectric layer 31 and a groove 36A for the
vibration plate 30 in common between two rows of the pressure chambers 14
(see FIG. 2), the grooves 36A and 37A may be formed independently for
each row of the pressure chambers 14 as shown in FIG. 8.

Second Modified Example

[0078] Moreover, in a case where a terminal section 35B, to which a wiring
member such as a flexible printed wiring board is connected is formed on
the surface of the individual electrode 32, a groove 36B (37B) may be
formed to surround the pressure chambers 14 entirely as shown in FIG. 9.
In this case, the cross talk can be reduced even more effectively.

Third Modified Example

[0079] Furthermore, a groove 36C (37C) which extends in both of the left
and right sides along the edge of the pressure chamber 14 may be formed
only between the nearest pressure chambers 14 (between pressure chambers
14 adjacent to each other in the paper feeding direction (vertical
direction in FIG. 10)) as shown in FIG. 10.

Fourth Modified Example

[0080] In the piezoelectric actuator 3 in the embodiment described above,
the vibration plate 30 which serves also as a common electrode is
arranged on the lower side of the piezoelectric layer 31, and the
individual electrodes 32 are formed on the upper side of the
piezoelectric layer. However, the present invention is also applicable to
a case where the arrangement of the individual electrodes and the common
electrode is reversed. In this case, after forming the groove 36 in the
vibration plate 30 (groove forming step) and joining vibration plate 30
to the surface of the cavity plate 10 (joining step), an insulating film
40 formed of a ceramics material such as alumina and zirconia is formed
by a method such as aerosol deposition (AD) method, vapor deposition
method, or sputtering method (insulating film forming step), and the
plurality of individual electrodes 32 is formed on a surface of the
insulating film 40 in an area overlapping in a plan view with the
pressure chambers 14 (individual electrode forming step) as shown in FIG.
11. Then, the piezoelectric layer 31 is formed on the surface of the
insulating layer 40 by chemical vapor deposition (CVD) method or aerosol
deposition (AD) method similarly as in the embodiment (piezoelectric
layer forming step), and finally a common electrode 34 is formed on a
surface of the piezoelectric layer 31 in an area overlapping in a plan
view with the pressure chambers 14 (individual electrodes 32), by a
method such as screen printing, vapor deposition method, or sputtering
method (common electrode forming step). The joining step may be carried
out after the common electrode forming step.

Fifth Modified Embodiment

[0081] The vibration plate is not restricted to the one which is made of a
metallic material and is electroconductive, and may be a one which is
made of a non-electroconductive material such as silicon, a synthetic
resin, glass, or ceramics with a surface oxidation treatment performed
thereon. In this case, the plurality of individual electrodes 32 can be
arranged on the upper side of the piezoelectric layer 31 as in the
embodiments described above. However, since the vibration plate in the
fifth modified embodiment is not electroconductive, the vibration plate
cannot serve as the common electrode. Therefore, a step of separately
forming the common electrode on the surface of the vibration plate
becomes necessary. In other words, as shown in FIG. 12, after forming
grooves 36E in a non-electroconductive vibration plate 30E by etching,
pressing, or injection molding and joining the vibration plate 30E to the
surface of the cavity plate 10, a plurality of common electrodes 34 may
be formed on a surface of the vibration plate 30E in an area overlapping
with the pressure chambers 14 by a method such as screen printing, vapor
deposition method, or sputtering method. In a case where the plurality of
individual electrodes 32 are arranged on the lower side of the
piezoelectric layer 31 as in the fourth modified embodiment (refer to
FIG. 11) described above, since the manufacturing process is almost
similar to that in the fourth modified embodiment, the description of the
manufacturing process is omitted.

[0082] The first to third embodiments and the modified embodiments
described above are examples in which the present invention is applied to
an ink-jet head which discharges ink from the nozzle. However, the
liquid-jet apparatus to which the present invention is applicable is not
restricted to the ink-jet head. The present invention can be applied to
liquid transporting apparatuses such as various liquid-jet apparatuses
for forming a minute wiring pattern on a substrate by discharging a
conductive paste, or for forming a highly defined display by discharging
an organic illuminant on a substrate, and further for forming a micro
optical device such as an optical guided wave path by discharging an
optical resin on a substrate. The piezoelectric actuator according to the
present invention can be used as an optical switch or an optical
deflector plate for optical communication by providing an optical element
such as a mirror on the piezoelectric actuator. Or, the piezoelectric
actuator in the present invention can be used as a display unit in which
each operating section is a pixel. Further, the liquid transporting
apparatus may be used not only for ink but also for transporting various
liquids such as blood, water, and solvents.